The invention relates to a method for producing a horizontal bore in the ground and a horizontal drilling device for use in such a method.
Horizontal drilling devices are used to introduce supply and disposal lines into the ground in trenchless construction or to exchange already installed old lines in a trenchless manner.
There are many different horizontal drilling devices. Common are horizontal drilling devices in which a drill head is initially advanced angled into the ground by means of a drill rod assembly and starting from a drill boom positioned above ground until the drill head has reached the desired drilling depth. Then, the drill head is redirected into the horizontal position in order to carry out the horizontal drilling. The target point of such a horizontal drilling can for example be located in a target excavation pit which is excavated for this particular purpose or in a basement room or it can also be located above ground i.e., like the starting point, so that the drill head after a defined drilling progress is redirected into a diagonally upwards pointing direction, to let the drill head reemerge above ground.
After the drill head has reached the target point, it is often replaced for a widening device for example a conical widening body, to widen the previously generated (pilot) bore by means of the drill boom when retracting the drill rod assembly. This may involve attaching a new line to be drawn into the widening device, to draw the new line into the ground simultaneous with the widening of the pilot bore.
Horizontal drilling devices are also used to replace old lines in the ground in a trenchless manner. For this, in a first step the drill rod assembly is pushed by the drill boom along the old line (and in particular through an old line) and after reaching a target point, which can be located in a maintenance shaft of the sewage system, the front end of the drill rod assembly is connected with a widening device by which the old line is cut or burst when retracting the drill rod assembly, wherein the fragments of the destroyed old line are radially displaced into the soil. At the same time, a new pipe can be drawn into the old pipe. Destroying the old pipe an displacing the fragments of the old pipe allows the new pipe to have an outer diameter which corresponds to the outer diameter of the old pipe or even exceeds this diameter.
As an alternative, an adapter can be connected to the front end of the drill rod assembly which adapter engages on the rear end of the old pipe and pulls the old pipe out of the ground when retracting the drill rod assembly. This allows avoiding that fragments of a destroyed old pipe remain in the ground which may otherwise cause damage to the new pipe due to sharp-edged brakeage edges and the pressure exerted by the surrounding soil.
Horizontal drilling devices usually have a linear drive with which the drill rod assembly can be advanced and retracted within the ground. Further, a rotational drive is usually provided with which the drill rod assembly (and with this the drill head and widening head connected thereto) can be rotated. The rotation of the drill head or the widening device allows improving the advance in the soil.
Further, most of the steerable horizontal drilling devices require a rotation of the drill head to steer the drill head into a desired drilling direction. The drill heads of such horizontal drilling devices have an asymmetrically formed (for example slanted) drill head front, which leads to a lateral deflection of the drill head during movement of the drill head through the soil. When the drill head is simultaneously rotatingly driven when being advanced in the soil, the asymmetric configuration of the drill head has no influence on the straight drilling course, because the lateral deflection evens out over a rotation. On the other hand, when the rotation of the drill head is stopped and the drill head is exclusively advanced by pushing—optionally supported by strokes of a stroke device which is integrated in the drill head or in the drill boom—the asymmetric configuration of the drill head leads to a (constant) lateral deflection. This achieves an arched drilling course and as a result a change of the drilling direction.
Horizontal drilling devices which are exclusively intended for replacing old pipes which are already installed in the ground often have no additional rotational drive.
Horizontal drilling devices in which the drill boom is intended for positioning above ground, often can only be used in non-urban areas because the horizontal drilling devices have to be positioned at a considerable distance to the region in which the bore or the new line is to be introduced into the ground or in which an already existing old pipe is to be exchanged, due to the drilling distance required to reach the desired drilling depth. Oftentimes, corresponding space requirements are not available in built-up areas. A further disadvantage of such horizontal drilling devices is that these drilling devices which are commonly configured as self-propelled drill boom, cause significant crop damage which has to be remedied by a corresponding financial effort.
Because of these disadvantages, the trenchless line construction in built-up areas is still largely limited to the trenchless replacement of old pipes because the old pipes always extend between subterranean hollow spaces (in particular supply shafts and basement rooms) which are already present and which can be used for the positioning of the horizontal drilling device. Excavation work and as a result, crop damage can thus mostly be prevented. For this, horizontal drilling devices have been developed which are configured so that they can be positioned in a supply shaft or sewage system. Because new supply lines often are not to be installed along existing supply routes these horizontal drilling devices are often not available for newly installing supply lines.
From IDE 196 33 934 A1 a horizontal drilling device is known which is configured for use in small excavation pits with a square cross section of about 70 cm×40 cm and a depth of about 1 m to 1.5 m. These horizontal drilling devices include a frame whose dimensions roughly correspond to the cross sectional dimensions of the excavation pit and are lowered into the excavation pit. A part of the frame protrudes over the upper edge of the excavation pit. In the section of the frame which is located inside the excavation pit a combined linear/rotary drive is provided via which a drill rod assembly which is composed of individual rod assembly sections is advanced into the soil. The rod assembly sections which are successively screwed to the rear end of the already drilled drill rod assembly are supplied to the linear/rotational drive via a rod assembly lift which transports the rod assembly sections from a rod assembly magazine which is arranged in the upper section of the frame which protrudes over the edge of the excavation pit, to the linear/rotational drive.
The horizontal drilling device known from DE 196 33 934 A1 enables introducing bores into the ground starting from any desired starting position. Because only a relatively small excavation pit is required for the positioning of the horizontal drilling device and the horizontal drilling device can also be transported easily owing to the compact design, its use is associated with relatively small crop damages.
A disadvantage of the horizontal drilling device known from DE 196 33 934 A1 is that for this horizontal drilling device an exact orientation of the excavation pit to be excavated is required because the direction in which the bore is initiated starting from the horizontal drilling device, is essentially perpendicular to the two narrow sides of the excavation pit. In addition, only two bores in opposite directions can be carried out based on one excavation pit, namely in the two directions which are perpendicular to the two narrow sides of the excavation pit. Drilling in the two directions requires lifting the entire horizontal drilling device out of the excavation pit, turning it by 180° about the vertical axis and then lowering it again into the excavation pit.
Proceeding from this state of the art, the invention is based on the object to provide an improved horizontal drilling device. Further, an improved method for introducing a bore into the ground was to be provided. In particular, a method and a corresponding horizontal drilling device was to be provided which, based on a relatively small excavation pit, allows flexibly introducing horizontal bores into the ground.